The present invention relates to a disk brake apparatus for use in braking of a vehicle.
FIG. 14 shows states of clearances between brake pads and a disk rotor of a disk brake apparatus used in a vehicle of a first related art of the present invention. As shown in FIG. 14, during braking, the temperature of the disk rotor 1 used in the disk brake apparatus of the first related art increases due to contact of the disk rotor 1 with the brake pads 2 and 3 [hereinafter the right pad in FIG. 14(A) is also referred to as “inner pad 2”, and the left pad in FIG. 14(A) is also referred to as “outer pad 3”], and tilting of a braking surface, i.e., thermal gradient may occur [FIG. 14(A)], although the braking surface is perpendicular to an axis of the disk at normal temperature. In this case, upon stop of the braking operation, clearances are generated based on the position of the thermal gradient [FIG. 14(B)]. After a certain time has passed, the disk rotor 1 returns to the normal state or recovers from the thermal gradient [FIG. 14(C)]. Immediately after the braking operation is stopped [FIG. 13(B)], the clearance between the disk rotor 1 and the inner pad 2 is substantially equal to that between the disk rotor 1 and the outer pad 3. However, when the disk rotor 1 recovers from the thermal gradient [FIG. 14(C)], the clearances are different [see the solid line in FIG. 14(C)]. If the vehicle continues to run with the brake rotor 1 that has recovered from the thermal gradient in this way, so-called one-side wear may occur, leading to generation of disk thickness variation (DTV) of the disk rotor 1. The thickness variation may cause occurrence of judder (Brake Judder; hereinafter referred to as “judder”).
As disk brake apparatuses aiming to solve this problem, for example, there are known disk brake apparatuses disclosed in Japanese Patent Application Public Disclosure No. 2006-307994 (hereinafter referred to as “patent document 1”), and Japanese Patent Application Public Disclosure No. 2000-46082 (hereinafter referred to as “patent document 2”). In the disk brake apparatus disclosed in patent document 1, the clearance is adjusted so that the clearance is expanded to satisfy the equation (clearance)>(axial displacement distance+surface run-out).
As mentioned above, in the disk brake apparatus disclosed in patent document 1, the problem caused by the thermal gradient of the rotor is solved by expanding the clearance. However, the expansion of the clearance in the apparatus of patent document 1 causes various negative effects (nega) such as impaired responsiveness, deteriorated pedal feeling, rattle generation, and decreased cleanablility. Due to the presence of these negative effects, it is sometimes undesirable or impossible to employ the apparatus of patent document 1 under present circumstances.
In the disk brake apparatus disclosed in patent document 2, it is possible to prevent negative effects, which would otherwise be caused by expanding the clearance as mentioned above, by performing a clearance minimizing control. However, the disk brake apparatus disclosed in patent document 2 still has a drawback; that is, although it is possible to prevent negative effects which would otherwise be caused by expanding the clearance, a self-cleaning operation is regularly performed in this apparatus, whereby a change of temperature of a rotor is induced, which leads to an increase in thermal gradient, causing an adverse effect.